Arterial stiffness is a major mechanism by which cardiovascular disease drives cardiovascular risk. Increases in arterial stiffness in the arterial tree increases central systolic and pulse pressure, and load on the left ventricle, and decreases the perfusion pressure through the coronary arteries in diastole, thereby increasing the risk of heart attacks, heart failure and stroke.
PWV is a well-established technique for obtaining a measure of arterial stiffness in a section of artery between two locations in the arterial tree. The velocity of the pulse wave along an artery is dependent on the stiffness of that length of artery. Most commonly, PWV is measured between the carotid and femoral peripheral artery sites in order to provide a measure predominantly of arterial stiffness of the aorta. Aortic PWV increases with age, typically doubling between the ages of 30 and 60.
As living standards improve, the incidence of diseases that are closely affected by lifestyle, such as hypertension, obesity, diabetes and hyperlipidemia, progressively increase. Arteriosclerosis, due to abnormalities or degeneration of the arterial wall, is known to be a major complication that is associated with these diseases and one that can lead to cardiovascular events such as heart failure, heart attacks and stroke. As a result, cardiovascular disease and stroke are the leading cause of mortality and morbidity in industrialised nations. With these numbers increasing, the need for better early detection and treatment of cardiovascular disease is becoming a clinical priority. Historically, healthcare professionals focused primarily on treating patients who showed evidence of these diseases. For early detection and intervention to be successful, “at risk” patients who are still asymptomatic will need to be identified. Assessment and treatment of cardiovascular risk will not only delay the onset of the disease, but also reduce healthcare costs and improve quality of life.
PWV is considered the “gold standard” by clinicians for measuring arterial stiffness. In clinical studies the following findings have been reported and widely acknowledged:                PWV is suggested as a marker of arteriosclerotic load or cardiovascular risk;        Aortic PWV correlates with the severity of independently assessed diabetic complications;        Arterial stiffness increases with age and in subjects with hypertension, diabetes mellitus, atherosclerosis, and end-stage renal disease;        Aortic PWV is strongly associated with the presence and extent of atherosclerosis and with aortic structural breakdown and constitutes a forceful marker and predictor of cardiovascular risk in hypertensive patients; and        Aortic PWV is a strong independent predictor of cardiovascular and all-cause mortality in patients with end-stage renal disease on hemodialysis.        
Accordingly, aortic stiffness measurements are an important tool in identifying patients at high risk of the effects of cardiovascular disease. The ability to identify these patients leads to better risk stratification and earlier and more cost-effective preventive therapy.
A known system used to measure PWV is the Applicant's SphygmoCor PVx (Trade Mark) Pulse Wave Velocity system, which, in pulse wave velocity mode, measures the velocity of the blood pressure waveform between any two superficial artery sites. This system uses simultaneous measurements of a single-lead ECG and with a tonometer (pressure sensor) of the pressure pulse waveform sequentially in the two peripheral artery sites (e.g. carotid & femoral). This device has automated software analysis and database facilities and its simplicity of use makes it suited for physician's offices. Only one operator is required to use this system. However, this system requires two sequential measurements to be performed using the R-wave peak of the ECG as the intermediate time reference point, and as such is relatively time consuming and slightly invasive to the patient.
Another known PWV system is the Artech Medical Complior (Trade Mark) system, which uses simultaneous direct contact pressure pulse sensors applied to major arterial sites without the need for an ECG. This allows a simultaneous recording of the same pulse wave as it transits through the body, and then calculates the PWV, heart rate and pulse transit times. A disadvantage of this system is it uses a cross correlation algorithm that is prone to errors due to differing wave shapes at the two arterial sites.
Another known system is the Colin Medical, COLIN Vascular Profile VP-1000 (trade mark) system, which is a screening device for the non-invasive assessment of arteriosclerosis. This system uses “Waveform Analysis and Vascular Evaluation” WAVE (Trade Mark), technology and assesses arteries by PWV and ABI (Ankle Brachial Index). The two indices are obtained using simultaneous blood pressure and waveform measurements on all four limbs along with ECG and phonocardiogram tracings. Disadvantages of this system are it is expensive and bulky and incorporates a large distance correction for the upper and lower limbs as the pulse travels in opposite directions.